I recently worked as a Return Material Authorization agent for a fairly large company.
Guess what, they all screw up! However, on a percentage basis it is very very low.
Unfortunately, it has to happen to someone. It was your turn in the barrel.
I'm not trying to seem cold or insensitive. It's just the cold hard facts of the volume they all move.
I'm sorry it happened and I do hope your turn is up.

UPS just leaves packages to keep costs down, for a fee they will get a signature.
Making sure an address is inside is a great idea that can help when lost.
Making sure it is well packaged is probably the most important issue.

Better luck in the future,
KW_Counter